1. Field of the Invention
The present invention relates to a detector, and in particular relates to a detector applied in a fan system.
2. Description of the Related Art
Electronic systems generate heat based on the amount of data they process. Because some electronic systems provide fast and continuous operations, heat dissipation devices for these electronic systems become more important nowadays. Various heat dissipation products are provided for users. However, fan systems are currently popular among the most.
Referring to FIG. 1, a conventional fan system 1 comprises a motor 10, a driving unit 20, and a rotation speed detection unit 30. The driving unit 20 is electrically connected to the motor 10 and receives an input voltage VIN to drive the motor 10. The rotation speed detection unit 30 is electrically connected to the driving unit 20 to detect the rotation speed of the motor 10 and output an examined signal S1 through the driving unit 20. The examine signal S1 is input to a monitor device 2 to determine the operation states of the motor 10.
Referring to FIGS. 2A and 2B, when the motor 10 is under a normal operation state, such as normal rotation speed, normal current output, and normal work temperature. The examined signal S1 is a pulse signal or a pulse width modulation (PWM) signal. When the motor 10 is under an abnormal operation state, such as fan locked, uncontrolled rotation speed, and violent temperature variation. The examined signal S1 generates a spike signal Sa as shown in FIG. 2A, a high-level signal Sb as shown in FIG. 2B and a low-level signal Sc as shown in FIG. 2B according to restricted values of the driving unit 20. Therefore, the monitor device 2 generates a stop or restart command.
In general, the monitor device 2 can set the required signal according to user requirements, such as spike signal Sa, high-level signal Sb and low-level signal Sc. If the required signal is the spike signal Sa, moreover, have two or more spike signals. It is easy to decide that there are continuous pulse signals to output. Thus, determining the motor 10 operation states of motor 10 is failed so that the monitor device 2 can not send commands immediately. However, if the required signal is the high-level signal Sb or low-level signal Sc, it will be alternately changed therebetween while the magnetic poles of the motor 10 are switched. It causes the reading of the monitor device 2 to fail. The two conditions mentioned above generally exist in conventional fan systems. Accordingly, the disposition for a damage or abnormal operation of the motor 10 is necessary to improve.